This invention relates to the field of glow drivers and, in particular, to a connector and controller used for transmitting and controlling the delivery of electrical power from an energy supply to a glow plug when starting and running a model glow engine used in a radio controlled (RC) vehicle.
Small engines, such as those used in remote-controlled model airplanes, cars, boats, etc. are described as a glow engine because they are equipped with a glow plug. The glow plug, which includes a resistive circuit or glow element, is typically threaded into the engine so that the glow element is located in the combustion chamber of the engine. In operation, the glow element is used to facilitate the catalytic reaction between an air/fuel mixture and the glow element, which takes place within the combustion chamber. This reaction produces useful mechanical power used for powering the vehicle. In starting and operating a model vehicle, it is important to establish a proper temperature within the combustion chamber in order to ensure proper fuel combustion and for preventing “flame outs” of the engine, where the engine shuts off and must be restarted.
When the glow engine is operating at normal operating revolutions per minute (RPMs), the temperature of the engine is sufficient that the glow element remains hot and, thus, ensures that the combustion chamber remains hot and that ignition occurs when the gases in the combustion chamber are compressed. However, it can be a particularly difficult task to initially start glow engines when the glow element and the combustion chamber is cold. To start a glow engine in this condition, the glow element is initially heated by applying electricity, typically in the form of a battery powered glow driver, which is temporarily mounted to the stem of the glow plug and then removed once the engine has been successfully started.
While the glow driver heats the glow plug, which heats the combustion chamber, the user attempts to start the engine. In the case of a model airplane, for example, a user might use a field starter to turn the propeller. As mentioned above, once the engine starts operating, the heat from its operation is typically enough to ensure that the glow element and the combustion chamber remain hot and the electric power or glow driver is quickly removed in order to extend the life of the batteries and the resistive glow element in the glow driver. As such, ideally, electricity is provided to the glow plug very briefly and only as long as necessary for the engine to be successfully started.
One issue, however, relates to when starting has actually occurred. In particular, there is a difference between (1) an engine that is turning due to an outside force (such as a field starter) and is not running under its own power (i.e., a non-running RPM or NR-RPM) and (2) an engine that is turning and running under its own power (i.e., a running RPM or R-RPM). The engine is successfully started and the glow driver should be removed only after there is a running RPM of the engine. If the glow driver is removed too early, the temperature of the combustion chamber may not be sufficiently hot and the engine may not start successfully.
In addition to the initial starting as discussed above, maintaining a proper temperature in the combustion chamber is also important during the operation of the vehicle in order to ensure a proper glow element temperature to ensure continued ignition of the fuel. This is particularly important for model planes or model boats, where losing power could cause the vehicle to crash or become stranded in a body of water. If the combustion chamber becomes cold, the glow plug will also become cold when it is not being heated by some external energy source, such as a battery as discussed above. This reduction in combustion chamber and glow plug temperature might occur for a number of reasons. For example, if the engine is idling for an extended period of time, such as during the landing portion of the flight, if the ambient temperature drops, or if an excessive amount of fuel enters the system and causes rapid cooling or flooding to occur. Once the glow plug becomes cold, there is a chance the air/fuel mixture will not combust and the engine will flame out. In that situation, it is unlikely that engine will maintain ignition if the on-board glow driver is not activated. However, as mentioned above, glow drivers, which provide electrical power to heat the glow plug, are often removed after the engine has been initially started. As such, one problem associated with the removal of the glow driver is that these engines lack the ability to correct a drop in combustion chamber temperature that takes place during the operation of the engine.
Prior devices have included a variety of connection means for connecting a power source to a glow plug. For example, certain prior connectors were comprised of a pair of alligator-type clips, each connected by a wire to one side of a battery. At the opposite end of the wires, one clip was attached to the glow plug stem and the other clip was attached to the body of the glow plug or the engine. One disadvantage with this design is that several steps were required to connect the various wires between power source and the glow plug.
Other devices have endeavored to simplify the connection process by providing a connector that can be mounted to glow plug at one connection point. For example, one such as the device is disclosed in U.S. Pat. No. 3,435,404. The device in the '404 patent includes a snap on connector that includes a contact point that is spring mounted, which contacts the stem of the glow plug. One major disadvantage of the design of the '404 patent is that the spring and contact point fails to provide a rigid, stable connection with the glow plug, which allows the connector to move, vibrate, rotate, etc., which is exacerbated during the use and operation of the engine. This becomes apparent when taking voltage readings, because taking these readings with a loose connection tends to create electrical noise leading to erroneous data.
As discussed below, taking voltage readings from a glow plug connector is important because these readings provide valuable information about the operation and state of the glow plug. Obtaining accurate data, with little or no noise, is also important because providing better data to the controller will enable the system to operate more effectively.
What is needed, therefore, is a device that enables a glow engine to be heated during the start-up phase and the use or running phase and that is capable of distinguishing between a running and non-running state.